(from Audi Press
Release) 240 kW (326 bhp): With this extremely impressive
power output, the new Audi A8 4.2 TDI quattro puts itself ahead of
all the other diesel-engined cars on the international market. The
entirely redeveloped 4.2-litre, eight-cylinder biturbo engine
accelerates the lightweight saloon with its aluminium body from 0 to
100 km/h (0  62 mph) in just 5.9 seconds. The top speed is
electronically restricted to 250 km/h. In addition to these dynamic
qualities, the new power plant displays the kind of refinement that
sets standards even in the top segment of the motoring world, and
ennobles the A8 4.2 TDI quattro, turning it into the perfect
long-distance touring saloon.

The new engine is also exemplary in terms of economy. Combined as
standard with quattro permanent four-wheel drive and 6-speed
tiptronic transmission, it uses on average just 9.4 litres of diesel
fuel for every 100 kilometres. This means it will cover more than
950 kilometres (590 miles) on a full tank without a stop.

The Audi A8 4.2 TDI quattro is equipped as standard with a diesel
particulate filter, which works without additives and consequently
lasts the lifetime of the vehicle without servicing.

The A8 4.2 quattro has a chassis with air suspension and adaptive
damping  otherwise known as Audi adaptive air suspension. It allows
the vehicle to be driven either in a decidedly sporty fashion or
with an extremely comfortable ride, just as the driver wishes.

Like the other A8 models, the new TDI has the exclusive front end
with single-frame radiator grille. The luxury saloon can be ordered
from beginning of June either with the standard wheelbase or in its
long-wheelbase version, which is 130 millimetres longer. First
deliveries will take place in the third quarter of 2005. The basic
price of the A8 4.2 TDI quattro in Germany is  81.000.

The sheer power and the characteristics of this eight-cylinder power
unit once again reaffirm the credentials of the Audi A8 as the
sportiest saloon car in the luxury segment. And thanks to its
top-of-the-range TDI, Audi yet again demonstrates its expertise and
its lead in the development of such powerful, refined and, not
least, economical diesel engines.

Entirely redesigned engine

The predecessor of the
new A8 4.2 TDI had already scored top marks among the luxury-class
diesel saloons with its 4-litre, eight-cylinder engine. Thanks to
its 275 bhp and 650 Nm of torque, it was the most powerful V8
diesel-engined car for a long period following its debut in the
summer of 2003. Its fuel consumption figures of just 9.6 litres per
100 km also earned it a top place among its competitors. With these
features the A8 4.0 TDI succeeded in becoming the European number
one among the V8 diesel luxury saloons, with a market share of 71 %.

In the light of such statistics, the development goals for the new
TDI represented a daunting challenge:

In order to implement these specifications, Audi's TDI development
team designed an entirely new engine. Just like the 3.0 and 2.7 TDI
before it, the 4.2-litre V8 TDI is a member of Audi's new family of
V-format engines, and has chain-drive for the camshaft and
ancillaries.

The cylinder spacing in the new engine block is now 90 millimetres.
This gives the engine a compact overall length of just 520
millimetres. One current competitor V8 with the same engine capacity
measures all of 140 millimetres more.

The engine block weighing 62 kg altogether is made of vermicular
graphite cast iron (GGV)  an important factor in achieving the low
engine weight of only 255 kilograms. This is 15 kilograms less than
its predecessor, the 4.0 TDI.

The 4.2 TDI is thus one of the lightest V8 diesels ever. This
benefits the power-to-weight ratio and the weight distribution in
equal measure  two characteristics that are of central importance
for the driving dynamics of the new A8 4.2 TDI quattro.

With an engine capacity of 4,134 cc, the combustion chambers of the
new engine are almost exactly 0.2 litres bigger than in the case of
the 4.0 TDI. The bore has been enlarged by 2 mm compared with its
predecessor, to 83 millimetres, and the stroke of 95.5 millimetres
is identical with that of the 4.0 TDI. The compression ratio is 16.5
: 1.

The surfaces of the cylinder bores are treated using UV laser
exposure. This special honing process ensures significantly reduced
oil consumption in the TDI engine, and, as a result, a significant
reduction in particulate formation during combustion.

The forged crankshaft made of chrome molybdenum steel is offset in
such a way that forces and moments of the first and second order are
avoided  a decisive bonus delivering extremely low levels of
vibration.

Chain drive for camshaft and
ancillaries

The cylinder head is
made of aluminium, and two camshafts are used to operate the valves
in each. They are driven via a maintenance-free chain drive, which
also drives the oil, water and power-assisted steering pumps.

There are four valves per cylinder, for optimum charging of the
combustion chamber. The valves on the new V8 are operated by roller
cam followers with hydraulic valve clearance compensation. This
low-friction drive technique plays a decisive part in reducing both
the fuel consumption and the emissions of the 4.2-litre engine.

The use of roller cam followers is likewise beneficial to the
engine's acoustics. In conjunction with the twisted-type and
therefore virtually play-free camshaft drive, these followers are
instrumental to the reduction in mechanical noise from the valve
gear and contribute to the 4.2 TDI's outstandingly quiet running.

The rigid construction of the engine block and the units effective
encapsulation also help to lessen the sound emitted by the
eight-cylinder engine.

Biturbo with two intercoolers

A concept that has
already proven its worth on the 4.0 TDI engine. Two turbochargers
with variable turbine geometry deliver high torque even at low
engine speeds, in conjunction with high power output.
Variable turbine geometry means that the flow of exhaust gas to the
turbine rotor can be optimised depending on load and engine speed.
By means of air mass metering, the engine management ensures that
both turbochargers run constantly at the same speed and therefore
achieve the same delivery rate. Maximum boost pressure is 2.5 bar;
the turbochargers rotate at up to 226,000 revolutions per minute.

The variable turbine geometry is supported by electrically operated
actuators on the new 4.2 TDI. These actuators adjust the vanes
faster and more precisely: particularly at low engine speeds, this
means a more rapid build-up of boost pressure, thus achieving an
excellent response.

The 4.2 TDI has two intercoolers, arranged on the right and left in
front of the engine. They are ideally positioned in the airflow
beneath the headlights, and are therefore capable of operating
extremely efficiently.

Each of the two turbochargers serves one bank of cylinders. The two
intake manifolds are interconnected by means of a "feedthrough"
system, to equalise the pressure between the right and left cylinder
banks. This feature boosts cylinder charging and consequently
enhances the engine's output.

There are continuously variable swirl flaps integrated into the
intake tract. These permit the air movement to be adjusted to suit
the engine speed and load at the time. High tumble at low engine
load results in optimised combustion, just as low tumble does at
high engine load.
In practice this means that a closed swirl duct at low load
increases swirl, while open ducts at high load boost cylinder
charging.

Common rail technology with piezo
injectors

The Bosch EDC16 CP
system, with fuel delivery, trigger-start, boost pressure and
exhaust-gas recirculation control, is responsible for engine
management on the V8 TDI. As on the A8 with a petrol engine, this
electronic system now means that it is possible to start the engine
automatically at the push of a button.

Mixture preparation is by means of a latest-generation common rail
system. It has a high-pressure pump  located inside the V of the
engine  and one pressurized pipe or "rail" for each cylinder bank.
The maximum injector pressure is now 1,600 bar, 250 bar more than
with previous common-rail systems, a value that corresponds with the
weight of a medium-sized saloon on the surface area of a fingernail.

This high injection pressure results in even finer atomisation of
the fuel and therefore in better mixture preparation and more
efficient combustion. The consequence is not merely extra power and
torque, but also reduced fuel consumption and emissions.

The piezo inline injectors are undoubtedly the most important
innovation of the new common rail system. Electrically excitable
piezo crystals undertake the triggering of the injectors. As soon as
a voltage is applied to the crystals,
they contract and, assisted by a hydraulic element, mechanically
trigger the opening of the injector needle.

The piezo injectors offer multiple advantages compared with
conventional solenoid valves. The moving masses on the injector
needles can, for instance, be reduced by no less than 75 percent,
from sixteen to four grams in each case.

This enables considerably smaller and more precisely metered
injection quantities. At the same time, piezo technology permits a
higher injector needle speed. With a value of 1.3 metres per second,
the piezo system responds twice as fast as other common rail
injectors.

The number of injection processes per combustion cycle can thus be
varied almost at will. In the case of the 4.2 V8, the Audi TDI
development team decided on up to four injections. In the lower
engine speed range there is a double injection in addition to the
main injection, and a single pre-injection in the mid-range.

This strategy produces a smoother combustion process, the benefits
of which are most immediately apparent in the engine's acoustic
behaviour. The 4.2 TDI engine has once again become significantly
quieter and smoother-running, even compared to its already highly
cultivated predecessor, and without doubt it sets the benchmark for
the class in this discipline.

The fuel is injected into the combustion chamber via eight-hole
jets. They too play a major part in making the combustion process
ultra-efficient, and thus improving the quality of emissions, by
distributing the fuel homogeneously throughout the combustion
chamber.

Highly effective exhaust emission
control

The 4.2 TDI has a
twin-pipe exhaust system with particulate filters as standard. In
each exhaust pipe the cleaning of the exhaust gases is undertaken by
an oxidising catalytic converter close to the engine and a
catalytically coated particulate filter.

The catalytic converter close to the engine ensures adherence to the
EU-4 limits by rapidly converting hydrocarbons and carbon monoxide.

The particulate filter, made of silicon carbide with thin-wall
technology, is located in the under-floor area. The combination of
thin-wall technology and catalytic coating enables controlled
regeneration from temperatures of approx. 580 ΊC, with
simultaneously low exhaust back pressure. This is reflected in only
marginally increased fuel consumption and enhanced regeneration
efficiency.

The A8 4.2 can cover distances of up to 2,000 kilometres before the
filter reaches its maximum charge level. The charge status of the
filter is continuously checked by means of monitoring of the exhaust
back pressure and parallel simulation calculation for both exhaust
pipes separately.

When regeneration becomes necessary, the engine management system
generates the required increase in temperature by means of measures
taken within the engine and exothermic conversion of unburned
hydrocarbons in the oxidising catalytic converter. Up to 5
injections are also possible with the common-rail injection system
used at Audi.

Top performance and impressive
fuel economy

The 4.2 TDI engine is
currently the most powerful diesel engine to be found in any
production saloon car. 240 kW (326 bhp) at 3,750 rpm are the new
benchmark  an increase of no less than 51 bhp over its 275 bhp
predecessor.

The A8 4.2 TDI quattro has the performance of a top athlete.
This lightweight luxury saloon with its aluminium body takes only
5.9 seconds to sprint from a standstill to 100 km/h  making it
quicker than any other diesel saloon on the international market. It
is capable of a governed top speed of 250 km/h.

The torque gives the driver a feeling of pulling power in every
speed range that is otherwise only to be experienced in a sports
car. 650 Newton-metres between 1,600 and 3,500 rpm  this
figure makes the A8 4.2 TDI quattro the Audi with the most torque of
them all.

Despite the 51 bhp increase in engine output, the new Audi A8 4.2
TDI quattro consumes no more fuel than its predecessor  quite the
opposite,in fact: Average consumption of just 9.4 litres / 100 km
means a cut in fuel consumption of 0.2 litres  a figure that is
nothing less than sensational!

Audi A8 4.2 TDI quattro: Supreme
sportiness

All Audi A8 V8 TDI
models are equipped with 6-speed tiptronic transmission with DSP
dynamic gearshift programme and additional sports programme. The
engine's output and torque are always unleashed with such precision
that the conflicting requirements of spontaneous power flow, high
performance and perfectly refined running are all achieved.

The Audi A8 has an aluminium chassis with four-link front suspension
and self-tracking trapezoidal-link rear suspension. Adaptive air
suspension  an air suspension system with continuous damper control
 provides the driving characteristics suitable for every driving
situation. It simultaneously reduces body movement, thus optimizing
road holding and comfort.

With its combination of a powerful TDI, highly developed lightweight
construction and the dynamic qualities of its suspension, the Audi
A8 4.2 TDI presents itself as a luxury saloon offering a new level
of sporty dynamism and superiority.